1. Technical Field
This invention relates to wiper systems and, more particularly, to a drill pipe wiper system for removing moisture from an outer surface of an existing drill pipe while the existing drill pipe is being removed from a ground surface.
2. Prior Art
Well drilling units are employed in prospecting for gaseous and liquid minerals and for bringing them to the surface. Because of the need for drilling to greater depths, as well as improving the speed of the drilling operation, traditional precision drilling techniques have been superseded by continuous rotary drilling. Rotary drilling utilizes rotational motion of a bit to drill the well bore. The bit is attached to a drill string which is comprised of drill collars, a drill pipe and a kelly joint. At the surface, rotational motion is imparted on the drill string by a rotary table to which the kelly joint is attached.
The drill cuttings produced by the bit that operates at the bottom of the well bore are carried to the earth's surface by circulating drilling fluids, i.e. drilling mud. That is, the drilling fluids are continuously pumped down the well bore through the kelly joint, and the drill pipe and the bit are recirculated to the surface. As drilling progresses, new joints of drill pipe are added. This process is commonly known in the art as “making a connection”.
Conversely, the drill string must also be removed periodically to replace worn bits and damaged drill pipe. This process in commonly known in the art as “tripping out”. Tripping out is performed by removing two to four joints of drill pipe at a time, depending upon the size of the derrick of the well drilling unit. A consequence of tripping out is spillage of drilling fluids because as the drill pipe is removed from the well bore drilling fluids drain from the inside and outside of the drill pipe. The spillage results in drilling fluids being wasted and rig workers being exposed to unsafe working conditions.
To prevent fluid drainage from the drill pipe during tripping out, pipe wipers have herefore been utilized to wipe the outside surface of the drill pipe as the drill pipe is hoisted out of the well bore. However, when employing the housing assemblies of the prior art to support the pipe wipers problems have been encountered in that the drilling fluids are not uniformly removed from the outside surface of the drill pipe. For example, when the shims are removed from the rotary table in order to allow tripping out of the drill pipe, the drill pipe can vertically move or sway which results in uneven wiping of the external surface of the drill pipe, as well as causing excessive wear on the pipe wipers.
U.S. Pat. No. 5,921,316 to McMinn discloses an automatic pipe wiping system using a circular air manifold with jets which are automatically triggered to flow air at the pipe. The pipe is wiped, even when moving laterally with crooked pipe. The pipe is air blown to wipe the mud down. The air jets have a pneumatic logic circuit that senses upward pipe movement and starts air flow to a manifold around the pipe. Unfortunately, this prior art example does not provide a means for quickly changing a wiper pad during operation of the system.
U.S. Pat. No. 5,842,252 to Cameron discloses a pipe wiper assembly for stripping fluid from oil and gas well strings which has a pair of rams which can move from a first remote position relative to the pipe forward to a second position contacting and wiping the pipe and forward to a third position when the pipe is not in the oil or gas well to protectively cover the well. The rams are mounted in a carrier which has freedom of movement in any radial direction to allow the rams to be centralized around the oil or gas well string. The unit also has alignment guides such that when the rams are returned to the first position, the rams and carrier will be centralized over the well bore and the freedom of radial movement is eliminated. Unfortunately, this prior art example does not provide a means for quickly changing a wiper pad during operation of the system.
U.S. Pat. No. 5,170,853 to Mason discloses a pipe wiper assembly that comprises a first housing for supportingly receiving at least one resilient wiper member. A second housing is supported above the well bore for connecting the first housing to the stack assembly of the drilling unit. The first and second housings are interconnected such that the first housing is selectively movable in response to vertical deviations of the drill pipe as the drill pipe is withdrawn from the vertically extending well bore. Unfortunately, this prior art example does not provide a means for collecting the wiped fluid and redistributing said fluid back into the circulation system.
Accordingly, the present invention is revealed in order to overcome the above noted shortcomings. The present invention satisfies such a need by providing a system that is convenient and easy to use, durable in design, and designed for removing moisture from an outer surface of an existing drill pipe while the existing drill pipe is being removed from a ground surface. The drill pipe wiper system includes a mud skirt for directing the flow of wiped fluids back into the circulation system. In addition, the wiper pads can be quickly replaced when needed, even during operation of the drill. The present invention is simple to use, affordable, and designed for many years of repeated use.